Back pressure relief apparatus



May 6, A941. 0. ROY 2,240,801

BACK PRESSURE RELIEF APPARATUS Filed July 16, 1940 2 Sheets-Sheet l I Inventor JVizZe flay Attorney:

' y 9 o. ROY 2,

BACK PRESSURE RELIEF APPARATUS Fi led July 16, 1940 2 She'ts-Sheet 2 Inventor Patented May 6, 1941 UNITED STATES PATENT OFFICE 2 Claims.

The present invention relates to improvements in back pressure relief apparatus for steam engines.

An object of the invention is the provision of back pressure relief apparatus for steam engines of generally improved design.

Another object of the invention is the provision of back pressure relief apparatus which is fully automatic in operation.

A further object of the invention is the provision of back pressure relief apparatus which is eflicient, reliable and positive in operation.

Still another object of the invention is the provision of back pressure relief apparatus of the aforesaid character, which isrelatively simple and inexpensive in construction.

Other objects and advantages of the invention will become apparent as the description progresses.

In the accompanying drawings forming a part of this specification and in which like reference characters are employed to designate corresponding parts throughout the same:

Figure 1 is a fragmentary longitudinal section through a steam engine showing my improved apparatus operatively associated therewith,

Figure 2 is a similar view showing the slide valve in reverse position,

Figure 3 is a transverse section taken on the line 33 of Figure 2, and

Figure 4 is a fragmentary transverse section through the steam chest.

Referring to the drawings, wherein for the purpose of illustration is shown a preferred embodiment of the invention, E generally designates a conventional steam engine having a steam chest l in which is mounted a slide valve II of the internal admission piston type. The steam is admitted to the chest l0 through a centrally connected supply pipe I2 and is admitted to a main cylinder l3 through admission and exhaust passages M for the operation of a working piston l5. Said passages communicate with the chest l0 by means of an annular groove l1 having a plurality of circumferentially spaced ports 26 opening in said chest, in the conventional manner. In the top of the steam chest I0 are provided a pair of exhaust ports "5 disposed adjacent the ends thereof and in communication with the annular groove l1.

Mounted on the chest [0, in registration with the ports l6 thereof, are a pair of relief valves F and G, each of which embodies an elongated cylindrical casing composed of an inner section I8 and an outer section [9. The inner 1 spider supporting a slide bearing 2|.

section is formed with an inwardly directed annular flange bevelled at the underside to form a valve seat 20 while just above the same, in the outer section, is secured a transversely arranged At the outer end of each casing is formed a longitudinal extension 22 formed with an axially arranged bore forming the bearing for the outer portion of an axially arranged slidable valve stem 23, the inner end of the stem being supported in the bearing 21. On the inner extremity of the stem is formed a bevelled valve disc 24 adapted to tightly engage the seat 20 in closed position. On the intermediate portion of the stem 23 is formed or secured a relief valve piston 25 adapted to reciprocate longitudinally in the upper portion of the outer casing section l9.

To the lower portion of the casing section I9 is connected one end of a pipe 21 which extends to and connects with the upper portion of the complementary casing section of valve G to afford communication between these casing sections. To the intermediate portion of the pipe 2? is connected, through the medium of a fitting 28, a feed pipe 29 which extends through the side of the steam chest I0 and communicates With the interior thereof on the inner steam feed side of the piston valve H. A complementary pipe 30 connects the upper portion of the casing of valve F with the lower portion of the casing of valve G, this pipe making communication with the steam chest through a branch pipe 3|. A loop line of piping, indicated at 32, connects the upper piston chamber of relief valve F with the lower piston chamber of relief valve G and makes communication with the exhaust end of the steam chest through a connecting pipe 33. A complementary loop 34 connects the upper portion of the piston chamber of relief valve G with the lower portion of the piston chamber of relief valve F and connects with the exhaust chamber at the opposite end of the steam chest through a pipe connection 35. To the lower portion of the valve chambers of both relief valves F and G are connected a pair of conduits 38 and 3? converging for connection with a Y- fitting 38 to which is also connected a carry-off pipe 39 which may relieve into a chimney-stack or the like 40, wherein a depressed atmosphere exists.

It is important to note, here, that the piping and conduits above described, and having reference characters from 2'! to 39, are in reality pipes having a substantial cross-section of the order of that of ports l6, for instance, although they are shown in the drawings on a smaller scale to simplify the representation which is, thus, more or less schematic. Since the entire exhaust steam must circulate through some of said piping, it is evident that it must be of suitable size to prevent back-pressure.

During operation,with the slide valve H in its extreme left end position as shown at Figure 1, the working fluid such as steam enters the steam chest l through the feed pipe I2 and passes through the centre portion of the steam chest through uncovered ports 26 into the left end passage [4 to actuate the working piston l5 which is thus moved toward the right hand end of the cylinder 13. In this position the left end piston head of the slide valve covers the steam chest connection of the conduit 35, and the conduit 3| is likewise closed by the right end piston head. The inlet of the pipe 29 is open, however, and communicates with the intermediate live steam section of the chest, so that steam is admitted to the relief valve F below the piston 25 so as to move the said piston 25 outwardly and seat the valve disk 20 to tightly close the relief outlet port at the 'left end of the chest. The closing of said valve therefore prevents the escape of live steam under pressure through the left port 25, which is in communication with groove ll. Simultaneously therewith steam entering the pipe 29 traverses the pipe 21 and enters the upper portion of the piston chamber of the valve G to slide the piston 25 of this valve inwardly and effect full opening of the relief valve at the right end, said valve being opened to permit exhaust of steam therethrough during the next operative cycle. The steam is conducted from the upper end of the chamber of valve Gr through the loop line 34 and enters the lower chamber of valve F from which it is exhausted through pipes 36 and 39;

While the slide valve l i is in this left end position the back pressure created'in the main chamber l3, by the movement of the piston I5, is initially relieved by passage through the right handpassage-way' M through the right end annular groove ll of the steam chest, and through the port it from whence it is exhausted through the open valve 24, pipe 3'! and discharge pipe 39, the latter preferably being disposed so that its outlet is in vacuum condition in a stack or the like. Further movement of the'piston IE, to the right, finally has the effect of'causing corresponding movement of the slide valve, due to the interlinked connection common to steam engines. Therefore, as the slide valve starts to move to the right, in preparation for the next movement of the piston IS, the right ports 26 are covered and the steam in the chest can only escape then through the conduit 33 which is covered the last,

said steam being relieved through the relief valve G and the pipe 31'.

When the slide valve ll moves to the opposite position at the right hand end of the steam chest,

as shown at Figure 2, the operation is reversed with feed steam entering the pipe 3| and passing therefrom through the pipe 30 into the top and bottom parts of the piston chamber of the relief valves F and G respectively, effecting closure of the valve G and opening the valve F so that back pressure is relieved through the left end of the steam chest and the exhaust port controlled by the relief valve F.

This provides automatically operative means for accurately regulating the relief of back pressure from a steam engine, enabling attainment of the maximum efficiency from the viewpoint of fuel utilization and control, and affording a structure which is reliable in operation without being unduly complicated or expensive.

It is to be understood that the form of my in vention herein shown and described is to be taken as a preferred example of the same, and that various changes as to the shape, size and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.

Having thus described my invention, I claim:

1. In combination with a steam engine having a slide valve in a steam chest and exhaust ports on said chest, auxiliary relief valves controlling the flow of fluid through said exhaust ports, means for actuating said valves, secondary steam inlet and exhaust ports adapted to be covered and uncovered through the action of the slide valve, and piping means between said relief valves and secondary ports and valve-actuating means whereby the valves will be operated in proper sequence according to the movements of the slide valve to admit and exhaust steam to the engine proper and exhaust steam from the steam chest after the exhaust ports are closed by the slide valve.

2. The combination with a steam engine having a steam chest, exhaust ports'on said chest and a slide valve reciprocable within said chest, of piston-actuated valves for opening and closing said exhaust ports, secondary steam inlet ports opening into the steam chest adjacent the exhaust ports and adapted to be covered and un-' covered by the slide valve, piping connecting said inlet ports with the piston valves for closing the same, secondary exhaust ports in the chest disposed nearer the ends thereof than the exhaust ports proper, conduits connecting said secondary exhaust ports with the piston valves, and a main exhaust pipe connecting piston valves with a source of vacuum or the like.

' OVIDE ROY. 

